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The Linux Kernel Power Problems On Older Desktop Hardware

06-22-2011, 11:10 AM

Phoronix: The Linux Kernel Power Problems On Older Desktop Hardware

As mentioned last week, a plethora of Linux power tests are on the way now that we have found an AC power meter with USB interface that works under Linux and we've been able to integrate nicely into the Phoronix Test Suite and its sensor monitoring framework. In this article is one of the first tests that have been completed using this power-measuring device as we monitored the Linux kernel power consumption for an old Intel Pentium 4 and ATI Radeon 9200 system for the past several kernel releases. Even this very old desktop system looks to be affected by the kernel power problems.

In terms of the power regressions that we have been tracking down, they are confirmed by this test.

I don't see it. The way I read that graph is that in .32 and .33 the desktop was not stepping down the power, and was going full bore all the time. In .34 this power management was introduced for the desktop. Then it looks like, from .35 onwards, the stepping up was made more sensitive to increased performance needs, going to full power. This would be to prevent people experiencing stutter, or poor experience with the system stepping up and down constantly.

Comment

For p4 the p4-clockmod module only manipulates the fsb. This is not the way as more current cpus work, there the fsb is not changed but the multiplyer in the cpu together with the vcore - these features are called (E)IST/(Enhanced) Intel Speed Step or Powernow (for AMD). Most likely the fsb change did not work on your system with kernel .32/.33, but using intel core cpus it should work - or amd athlon 64 and newer. You should take this info into account when you look at the values.

Comment

I don't see it. The way I read that graph is that in .32 and .33 the desktop was not stepping down the power, and was going full bore all the time. In .34 this power management was introduced for the desktop. Then it looks like, from .35 onwards, the stepping up was made more sensitive to increased performance needs, going to full power. This would be to prevent people experiencing stutter, or poor experience with the system stepping up and down constantly.

Comment

I don't see it. The way I read that graph is that in .32 and .33 the desktop was not stepping down the power, and was going full bore all the time. In .34 this power management was introduced for the desktop. Then it looks like, from .35 onwards, the stepping up was made more sensitive to increased performance needs, going to full power. This would be to prevent people experiencing stutter, or poor experience with the system stepping up and down constantly.

Comment

I mean, you've been "tracking down" this issue for ... I don't know, more than a month now. The fact that you're compiling the kernel on a slow laptop really doesn't sound like a fair excuse anymore. Or are you just still keeping the results for yourself?

Comment

I mean, you've been "tracking down" this issue for ... I don't know, more than a month now. The fact that you're compiling the kernel on a slow laptop really doesn't sound like a fair excuse anymore. Or are you just still keeping the results for yourself?

He wanted to wait til he got the power meter (last weekend) to finish bisecting all the power issues. Hopefully that also means he wants to do it properly, because then the kernel dudes might take it seriously and fix it (and I could move away from 2.6.37...)